This invention relates to an engine control system and method and more particularly to an improved system and method for controlling combustion and precluding knocking in engine performance.
A wide variety of sophisticated engine controls have been provided for improving engine performance. These engine controls provide a number of different advantages and control routines to achieve those advantages. Normally, the controls employ a system or methodology which prevents or reduces knocking in the engine. Knocking is a condition which occurs when the flame propagation is too rapid and spontaneous combustion or irregular combustion results. This provides not only unsatisfactory running conditions, but if prolonged, can actually cause engine damage.
Normally, the way knocking is avoided is by retarding the spark timing. Alternatively varying the amount of fuel supplied to the engine also is a way in which the knocking condition can be controlled. At times, both adjustments in spark timing and in fuel supply amount may be coupled together for the control.
The disadvantage with these previously proposed systems is that both tend to reduce the actual engine power output. However, the knocking condition generally occurs when the engine is called upon to produce a greater amount of power than normal. Thus, the reduction of power is counterproductive in the ability to obtain the desired performance.
It is, therefore, a principal object of this invention to provide an improved engine control system and method wherein knocking can be avoided or minimized and yet the engine power is not substantially reduced.
It is a further object of this invention to provide an improved method and system for operating an engine to provide knock control.
It is a further object of this invention to provide a knock control system and method for an engine that will nevertheless permit the attainment of relatively high power outputs.
The types of fuel supply systems utilized in engines fall into two general categories. One type of fuel supply system utilizes a carburetor as a charge former and thus provides an air-fuel ratio that is supplied to the engine and which does not vary significantly during a given intake cycle. The other type of system employs fuel injection, which injects a finite amount of fuel, generally once per cycle. This fuel is injected either into the induction system or directly into the combustion chamber. The fuel is generally sprayed in a single installment and hence, the actual combustion cycle in the combustion chamber is controlled primarily by the time at which ignition occurs. That is, the flame propagation and pressure buildup in the cylinder will be determined solely by the amount of fuel and the locale of the fuel patch in the combustion chamber.
Because of these factors, the engine performance cannot be totally controlled so as to provide optimum performance. That is, the combustion curve and pressure buildup in the combustion chamber is substantially fixed once the ignition time and fuel supply amount is set. This gives rise to rapid pressure buildup and high pressure peaks, which do not necessarily provide optimum performance.
It is, therefore, a still further object of this invention to provide a fuel supply system and control therefor for an engine wherein the pressure buildup in the combustion chamber during the combustion cycle can be more accurately controlled.